CN113674770A

CN113674770A - Magnetic disk device

Info

Publication number: CN113674770A
Application number: CN202011610120.5A
Authority: CN
Inventors: 矶川博
Original assignee: Toshiba Corp; Toshiba Electronic Devices and Storage Corp
Current assignee: Toshiba Corp; Toshiba Electronic Devices and Storage Corp
Priority date: 2020-05-14
Filing date: 2020-12-30
Publication date: 2021-11-19
Anticipated expiration: 2040-12-30
Also published as: US11984143B2; US20230245679A1; CN113674770B; US11651782B2; CN116153344A; CN116153343A; CN116153342A; JP2021180061A; US20210358517A1

Abstract

Embodiments provide a magnetic disk device capable of increasing a recording capacity in consideration of positioning accuracy of a magnetic head. A magnetic disk device of an embodiment includes: a plurality of magnetic disks having recording layers and arranged coaxially with spaces therebetween; and a plurality of magnetic heads having magnetic poles for generating a recording magnetic field in a direction perpendicular to the recording layer, the magnetic heads being arranged at intervals along the parallel direction of the magnetic disks. Among the plurality of magnetic heads, the magnetic head having a wider magnetic pole width of the magnetic pole in the width direction of the recording track formed in the recording layer, or the magnetic head having a wider area width in the width direction, which is capable of reading the magnetic characteristics of the area where the magnetic recording is performed on the recording layer by the magnetic head, is disposed at a position further away from the vicinity of the center in the parallel direction.

Description

Magnetic disk device

The present application enjoys priority based on Japanese patent application No. 2020-. The present application incorporates the entire contents of the base application by reference thereto.

Technical Field

Embodiments of the present invention relate to a magnetic disk device.

Background

As one means for increasing the recording capacity of a magnetic disk device, it is effective to increase the number of magnetic disks mounted in the device. However, when the mounting space is limited, the thickness of the magnetic disk and the distance between adjacent magnetic disks need to be reduced in order to increase the number of disks. Even when the thickness and the spacing of the magnetic disk are reduced, it is required that the frequency of occurrence of errors during writing or reading of data due to, for example, deterioration in positioning accuracy of the magnetic head is not increased. Since the positioning accuracy of the magnetic head is affected by torsion (torsion) or the like generated in the rotating shaft of the actuator when the magnetic head is driven, the magnetic head disposed on the cover side and the base side of the housing of the magnetic disk device is more likely to be degraded. That is, the positioning accuracy of the magnetic head differs depending on the position in the direction in which the magnetic heads are arranged (the parallel (side-by-side) direction).

Disclosure of Invention

Embodiments of the present invention provide a magnetic disk device capable of increasing a recording capacity in consideration of a position of a magnetic head in a parallel direction.

A magnetic disk device of an embodiment includes: a plurality of magnetic disks having recording layers and arranged coaxially with spaces therebetween; and a plurality of magnetic heads having magnetic poles for generating a recording magnetic field in a direction perpendicular to the recording layer, the magnetic heads being arranged at intervals along the parallel direction of the magnetic disks. Among the plurality of magnetic heads, the magnetic head having a wider magnetic pole width of the magnetic pole in the width direction of the recording track formed in the recording layer, or the magnetic head having a wider area width in the width direction, which is capable of reading the magnetic characteristics of the area where the magnetic recording is performed on the recording layer by the magnetic head, is disposed at a position further away from the vicinity of the center in the parallel direction.

Drawings

Fig. 1 is a block diagram schematically showing a Hard Disk Drive (HDD) according to an embodiment.

Fig. 2 is a side view schematically showing the magnetic head, the suspension, and the magnetic disk in the HDD.

Fig. 3 is an enlarged cross-sectional view showing a head portion of the magnetic head.

Fig. 4 is a perspective view schematically showing a write head of the magnetic head.

Fig. 5 is an enlarged cross-sectional view of the front end of the write head.

FIG. 6 is a plan view of the write head of the magnetic head viewed from the ABS side.

Fig. 7 is a diagram schematically showing an example of an arrangement of the magnetic disk and the magnetic head.

Fig. 8 is a diagram showing an example of the value of the magnetic pole width of each of the plurality of magnetic heads.

Fig. 9 is a diagram showing a relationship between a cross track position and a signal output, which are used when measuring the width of the magnetic characteristic of the main pole.

Fig. 10 is a diagram schematically showing a relationship between the number of times of recording (Write count) and the Error Rate (Error Rate) for the recording tracks of the magnetic disk.

Fig. 11 is a diagram showing an example of classification of the disk based on the overwrite characteristic (OW).

Fig. 12 is a flowchart showing an example of control of the recording current (recording current control processing) in the HDD.

Detailed Description

The magnetic disk device according to the embodiment will be described below with reference to the drawings.

The present invention is not limited to the above-described embodiments, and various modifications, and variations can be made without departing from the spirit and scope of the present invention. In addition, although the drawings schematically show the width, thickness, shape, and the like of each part in comparison with the actual form in order to clarify the description, the drawings are merely examples and do not limit the explanation of the present invention. In the present specification and the drawings, the same reference numerals are used for the same elements as those already described with respect to the previous drawings, and detailed description may be omitted or simplified as appropriate.

(embodiment 1)

A hard disk drive (hereinafter referred to as HDD) according to embodiment 1 will be described in detail as a magnetic disk device. Fig. 1 is a block diagram schematically showing an HDD according to embodiment 1, and fig. 2 is a side view showing a magnetic head and a magnetic disk in a levitated state.

As shown in fig. 1, the HDD10 includes a rectangular housing 11, a magnetic disk 12 as a recording medium disposed in the housing 11, a spindle motor 21 for supporting and rotating the magnetic disk 12, and a plurality of magnetic heads 16 for writing (writing) and reading (reading) data to and from the magnetic disk 12. The frame 11 includes a rectangular box-shaped base (not shown) having an open upper portion and a cover (not shown) covering the opening of the base. The base body is formed of, for example, a rectangular bottom wall and a side wall rising along the peripheral edge of the bottom wall, and is integrally molded of aluminum or the like. The cover is screwed to the side wall of the base by, for example, a plurality of screws, closes the opening of the base in an airtight manner, and is formed of stainless steel or the like.

The HDD10 includes a head actuator 18, and the head actuator 18 moves and positions the magnetic head 16 to an arbitrary recording track on the magnetic disk 12. The head actuator 18 includes a carriage assembly 20 that movably supports the magnetic head 16, and a voice coil motor (hereinafter, VCM)22 that rotates the carriage assembly 20.

The HDD10 includes a head amplifier IC30 that drives the magnetic head 16, a main controller 90, and a driver IC 92. The head amplifier IC30 is provided on the carriage assembly 20, for example, and is electrically connected to the magnetic head 16. The head amplifier IC30 includes a recording current supply circuit (recording current supply unit) 91 for supplying a recording current to a recording coil of the magnetic head 16, a bias voltage supply circuit 93 for supplying a bias voltage (drive current) to a spin torque oscillator (hereinafter referred to as STO) described later, a heater voltage supply circuit 98 for supplying a drive voltage to a heater described later, an amplifier (not shown) for amplifying a signal read by the magnetic head 16, and the like.

The main controller 90 and the driver IC92 are constituted by, for example, a control circuit board (not shown) provided on the rear surface (base) side of the housing 11. The main controller 90 includes an R/W channel 94, a hard disk controller (hereinafter, referred to as HDC)96, a microprocessor (hereinafter, referred to as MPU)97, and a memory 80. The main controller 90 is electrically connected to the magnetic head 16 via a head amplifier IC 30. The main controller 90 is electrically connected to the VCM22 and the spindle motor 21 via a driver IC 92. The HDC96 can be connected to a host 95.

As shown in fig. 1 and 2, the magnetic disk 12 is configured as a perpendicular magnetic recording medium. The magnetic disk 12 has a substrate 101 formed of a non-magnetic material and formed in a disc shape having a diameter of 88.9mm (3.5 inches), for example. On each surface (upper and lower surfaces) of the substrate 101, a soft magnetic layer 102 as an underlayer formed of a material exhibiting soft magnetic characteristics, a magnetic recording layer (recording layer) 103 having magnetic anisotropy in a direction perpendicular to the surface of the magnetic disk 12, and a protective film 104 are laminated in this order from the lower layer to the upper layer. The magnetic disk 12 and a hub (hub) of the spindle motor 21 are coaxially fitted to each other. The magnetic disk 12 is rotated in the arrow B direction at a predetermined speed by a spindle motor 21.

The carriage assembly 20 includes a bearing portion 24 rotatably supported by the frame 11, and a plurality of suspensions 26 extending (extending) from the bearing portion 24. As shown in FIG. 2, the magnetic head 16 is supported at the extended end of each suspension 26. The magnetic head 16 is electrically connected to the head amplifier IC30 via a wiring member (flexure) 28 provided to the carriage assembly 20.

As shown in fig. 2, the magnetic head 16 is configured as a floating type head, and includes a slider 42 formed in a substantially rectangular parallelepiped shape, and a head portion 44 formed at an end portion on the outflow end (tail) side of the slider 42. The slider 42 is formed of, for example, a sintered body of alumina and titanium carbide (AlTiC), and the head 44 is formed of a multilayer thin film. The slider 42 is attached to the gimbal portion 41 of the wiring member 28.

The slider 42 has a rectangular disk facing surface (air bearing surface (hereinafter, ABS))43 facing the surface of the magnetic disk 12. The slider 42 is maintained in a state of being suspended from the surface of the magnetic disk 12 by a predetermined amount by an air flow C generated between the disk surface and the ABS43 by the rotation of the magnetic disk 12. The direction of the air flow C coincides with the rotation direction B of the magnetic disk 12. The slider 42 has a leading end 42a on the inflow side of the air stream C and a trailing end 42b on the outflow side of the air stream C. As the magnetic disk 12 rotates, the magnetic head 16 moves relative to the magnetic disk 12 in the direction of arrow a (head moving direction), that is, in the direction opposite to the disk rotation direction B.

Fig. 3 is an enlarged cross-sectional view showing the head 44 of the magnetic head 16 and the magnetic disk 12. The head 44 has a read head (reproducing head) 54 and a write head (recording head) 58 formed on the trailing end 42b of the slider 42 by a thin film process, and is formed as a separate type magnetic head. The read head 54 and the write head 58 are covered with a nonmagnetic protective insulating film 53 except for a portion exposed at the ABS43 of the slider 42. The protective insulating film 53 constitutes the outer shape of the head portion 44.

The longitudinal direction of the recording track formed in the magnetic recording layer 103 of the magnetic disk 12 is defined as a trailing track (down track) direction DT, and the width direction of the recording track is defined as a cross track direction WT.

The read head 54 includes a magnetoresistive element 55, and a 1 st magnetic shield film 56 and a 2 nd magnetic shield film 57 which are arranged on the leading side (inflow side) and the trailing side (outflow side) of the magnetoresistive element 55 so as to sandwich the magnetoresistive element 55 in the track following direction DT. The magnetoresistive effect element 55, the 1 st magnetic shield film 56, and the 2 nd magnetic shield film 57 extend substantially perpendicularly with respect to the ABS 43. The lower ends of the magnetoresistive effect element 55, the 1 st magnetic shield film 56, and the 2 nd magnetic shield film 57 are exposed at the ABS 43.

The write head 58 is disposed on the trailing end 44b side of the slider 42 with respect to the read head 54. Fig. 4 is a perspective view of the write head 58 obtained by cutting the write head 58 at the center of the track, fig. 5 is an enlarged cross-sectional view showing the tip (ABS-side end) of the write head 58, and fig. 6 is a plan view of the write head 58 viewed from the ABS side.

As shown in fig. 3 and 4, the write head 58 includes a main pole (magnetic pole) 60 that generates a recording magnetic field in a perpendicular direction with respect to the surface of the magnetic disk 12, a trailing shield (write shield) 62 that is provided on the trailing side of the main pole 60 and faces the main pole 60 with a write gap WG therebetween, a leading shield 64 that faces the leading side of the main pole 60, a pair of side shields 63 that are provided on both sides of the main pole 60 in the cross-track direction CT, and a high-frequency oscillation element, such as a Spin Torque Oscillator (STO)65, that is provided between the main pole 60 and the trailing shield 62 in the write gap WG. The main pole 60 and the trailing shield 62 constitute a 1 st magnetic core forming a magnetic circuit, and the main pole 60 and the leading shield 64 constitute a 2 nd magnetic core forming a magnetic circuit. The write head 58 has a 1 st recording coil 70 wound around a 1 st core and a 2 nd recording coil 72 wound around a 2 nd core.

The main pole 60 is formed of a soft magnetic material having a high magnetic permeability and a high saturation magnetic flux density, and extends substantially perpendicularly to the ABS 43. The tip portion 60a of the main pole 60 on the ABS43 side narrows toward the ABS43 to a tip, and is formed in a column shape having a narrow width relative to other portions. The leading end surface of the main pole 60 is exposed at the ABS43 of the slider 42.

As shown in fig. 5 and 6, the tip end portion 60a of the main pole 60 has a flat trailing end surface 60b facing the trailing shield 62 with a gap therebetween. The distal end portion 60a is formed in a trapezoidal shape in cross section, for example. The trapezoidal tip (tip surface) 60a has a tail end surface 60b extending in the cross-track direction CT, a leading end surface 60c facing the tail end surface 60b, and two side surfaces 60 d. In the ABS43, the width of the leading end portion 60a, i.e., the width WP of the trailing end surface 60b in the cross-track direction CT substantially corresponds to the track width of the recording tracks on the magnetic disk 12. In the tip end portion 60a, the trailing end surface 60b and the leading end surface 60c may extend in a direction perpendicular to the ABS43, or may extend obliquely with respect to a direction perpendicular to the ABS 43. The side surfaces 60d extend obliquely with respect to the central axis C of the main pole 60, i.e., with respect to the tracking direction DT.

As shown in fig. 3 to6, the trailing shield 62 is made of a soft magnetic material and is provided to efficiently close a magnetic path via the soft magnetic layer 102 of the magnetic disk 12 directly under the main pole 60. The trailing shield 62 is disposed on the trailing side of the main pole 60. The trailing shield 62 is formed in a substantially L-shape, and a distal end portion 62a thereof is formed in an elongated rectangular shape. The front face of the trailing shield 62 is exposed at the ABS43 of the slider 42. The tip portion 62a has a leading side end surface (magnetic pole end surface) 62b facing the tip portion 60a of the main magnetic pole 60. The leading side end surface 62b is sufficiently longer than the width WP of the leading end portion 60a of the main magnetic pole 60 and the track width of the magnetic disk 12, and extends in the cross-track direction CT. The leading side end face 62b extends perpendicularly or slightly obliquely with respect to the ABS 43. In the ABS43, the lower end edge of the leading end surface 62b and the trailing end surface 60b of the main pole 60 are opposed in parallel with each other with a write gap WG (gap length along the track direction DT).

As shown in fig. 4 and 5, the trailing shield 62 has the 1 st connection portion 50 connected to the main pole 60. The 1 st connection portion 50 is magnetically connected to an upper portion of the main pole 60, i.e., a portion of the main pole 60 that is separated from the ABS43, via the non-conductor 52. The 1 st recording coil 70 is wound around the 1 st connecting portion 50 in the 1 st core, for example. When writing a signal to the magnetic disk 12, a recording current flows through the 1 st recording coil 70, and the 1 st recording coil 70 excites the main pole 60 to flow a magnetic flux through the main pole 60. The recording current supplied to the 1 st recording coil 70 and the 2 nd recording coil 72 is controlled by the main controller 90.

As shown in fig. 4 and 6, the pair of side shields 63 are disposed on both sides of the main pole 60 in the cross-track direction CT so as to be physically disconnected from the main pole 60 and connected to the trailing shield 62. In the present embodiment, the side shield 63 is formed integrally with the leading end portion 62a of the trailing shield 62 by a high-permeability material, and protrudes from the leading end surface 62b of the leading end portion 62a toward the leading end side of the slider 42.

As shown in fig. 3 to 5, a leading shield 64 formed of a soft magnetic material is provided on the leading side of the main pole 60 so as to face the main pole 60. The leading shield 64 is formed in a substantially L-shape, and the ABS 43-side front end portion 64a is formed in an elongated rectangular shape. The front end surface (lower end surface) of the front end portion 64a is exposed at the ABS 43. The trailing end surface 64b of the leading end portion 64a extends in the cross-track direction CT. In the ABS43, the trailing end surface 64b faces the leading end surface 60c of the main pole 60 with a gap. In the present embodiment, the leading end portion 64a of the leading shield 64 is formed integrally with the side shield 74 from a high permeability material.

In addition, the leading shield 64 has a 2 nd connecting portion 68 that is joined to the main pole 60 at a position apart from the ABS 43. The 2 nd connecting portion 68 is formed of, for example, a soft magnetic material, and is magnetically connected to an upper portion of the main pole 60, that is, a portion of the main pole 60 separated from the ABS43, via the non-conductive body 59. Thereby, the 2 nd connecting portion 68 forms a magnetic circuit together with the main pole 60 and the leading shield 64. The 2 nd recording coil 72 of the write head 58 is disposed so as to be wound around the 2 nd connecting portion 68, for example, and applies a magnetic field to the magnetic circuit.

As shown in fig. 5 and 6, STO65 functioning as a high-frequency oscillation element is provided between the leading end portion 60a of the main pole 60 and the leading end portion 62a of the trailing shield 62 in the write gap WG. The STO65 includes a spin injection layer 65a, an intermediate layer (nonmagnetic conductive layer) 65b, and an oscillation layer 65c, and is configured by stacking these layers in this order from the main pole 60 side to the trailing shield 62 side, that is, in this order along the tracking direction DT of the magnetic head 16. The spin injection layer 65a is joined to the trailing end surface 60b of the main pole 60 via a nonmagnetic conductive layer (under layer) 67 a. The oscillation layer 65c is joined to the leading end face 62b of the trailing shield 62 via a nonmagnetic conductive layer (cap layer) 67 b. The order of lamination of the spin injection layer 65a, the intermediate layer 65b, and the oscillation layer 65c may be reversed from that described above, that is, the layers may be laminated in order from the trailing shield 62 side to the main magnetic pole 60 side.

The spin injection layer 65a, the intermediate layer 65b, and the oscillation layer 65c each have a lamination surface or a film surface extending in a direction intersecting with the ABS43, for example, in a direction orthogonal thereto. At least the lower end surface of the oscillation layer 65c, in this embodiment, the entire lower end surface of STO65 including the spin injection layer 65a, the intermediate layer 65b, and the oscillation layer 65c is exposed at the ABS43, and extends coplanar (flush) with the ABS 43. Alternatively, the entire lower end surface of STO65 may be set back, i.e., may be located at a position away from ABS43, for example, in a direction perpendicular to ABS43 and toward the depth side. The lower end surface of STO65 is not limited to a flat surface, and may be formed in an arc shape protruding upward.

As shown in fig. 6, in the ABS43, the width WS in the cross-track direction CT of the STO65 is formed larger than the width WP of the trailing end surface 60b of the main pole 60 (WS > WP). In one example, the width WS of STO65 is about 1.1 to 1.6 times the width WP of the main pole 60. STO65 is disposed so as to cover at least one of end edges (end portions in the cross-track direction) EE1 and EE2 of the trailing end face 60b, i.e., so as to extend beyond the end edge to the outside of the main pole 60. In the present embodiment, STO65 is arranged symmetrically with respect to the center axis C, and covers both end edges EE1 and EE2 of the trailing end surface 60b in the cross-track direction CT. That is, both ends of STO65 in the cross-track direction CT extend outward of the main pole 60 beyond the end edges EE1 and EE2 of the trailing end face 60b, respectively.

As shown in fig. 4 and 5, the main pole 60 and the trailing shield 62 are connected to the connection terminal 45 via wires, and further connected to the head amplifier IC30 and the main controller 90 via the flexure 28. A current circuit is configured to supply an STO drive current (bias voltage) from the head amplifier IC30 through the main pole 60, STO65, and trailing shield 62 in series.

The 1 st recording coil 70 and the 2 nd recording coil 72 are connected to the connection terminal 45 via wires, and further connected to the head amplifier IC30 via the flexure 28. The 2 nd recording coil 72 is wound in the opposite direction to the 1 st recording coil 70. When writing a signal to the magnetic disk 12, a recording current is passed from the recording current supply circuit 91 of the head amplifier IC30 to the 1 st recording coil 70 and the 2 nd recording coil 72, and the main pole 60 is excited to pass a magnetic flux through the main pole 60. The recording current supplied to the 1 st recording coil 70 and the 2 nd recording coil 72 is controlled by the main controller 90. Further, the 2 nd recording coil 72 may be connected in series with the 1 st recording coil 70. The 1 st recording coil 70 and the 2 nd recording coil 72 may be controlled to supply current individually.

As shown in fig. 4, the magnetic head 16 may further include a 1 st heater 76a and a 2 nd heater 76 b. The 1 st heater 76a is provided in the vicinity of the main pole 60 in the vicinity of the write head 58, for example, between the 1 st recording coil 70 and the 2 nd recording coil 72. The 2 nd heater 76b is disposed in the vicinity of the read head 54. The 1 st heater 76a and the 2 nd heater 76b are connected to the connection terminal 45 via wires, and further connected to the head amplifier IC30 via the flexure 28.

When the HDD10 configured as described above is operated, the main controller 90 drives the spindle motor 21 via the driver IC92 under the control of the MPU97 to rotate the magnetic disk 12 at a predetermined speed. In addition, the host controller 90 drives the VCM22 via the driver IC92 to move and position the head 16 to a desired track on the disk 12. The ABS43 of the magnetic head 16 faces the disk surface with a gap. In this state, the magnetic disk 12 is read from the recording information by the read head 54 and written to the recording information by the write head 58.

When writing information, the bias voltage supply circuit 93 of the head amplifier IC30 applies a bias voltage to the main pole 60 and the trailing shield 62 under the control of the MPU97, and thereby supplies a drive current in series through the connection terminal 45, the wiring, the main pole 60, the STO65, and the trailing shield 62. The drive current flows in the direction perpendicular to the stacking surface of STO 65. STO65 oscillates spin torque to generate a high-frequency magnetic field, and the high-frequency magnetic field is applied to magnetic recording layer 103 of magnetic disk 12.

At the same time, the recording current supply circuit 91 of the head amplifier IC30 supplies a recording current to the 1 st recording coil 70 and the 2 nd recording coil 72 in accordance with the recording signal generated from the R/W channel 94 and the recording mode. The 1 st recording coil 70 and the 2 nd recording coil 72 excite the main pole 60 to generate a recording magnetic field, and the recording magnetic field in the perpendicular direction is applied from the main pole 60 to the magnetic recording layer 103 of the magnetic disk 12 located under the main pole. Thereby, information is recorded in the magnetic recording layer 103 with a desired track width. By superimposing the high-frequency magnetic field of STO65 on the recording magnetic field, magnetization reversal of the magnetic recording layer 103 can be promoted, and magnetic recording with high magnetic anisotropy energy can be performed.

The spin torque oscillated from STO65 is directed in the opposite direction to the direction of the gap magnetic field generated between the main pole 60 and the trailing shield. Thus, the spin torque acts to reduce leakage flux that flows directly from the main pole 60 to the trailing shield 62. As a result, the amount of magnetic flux from the main pole 60 toward the magnetic recording layer 103 of the magnetic disk 12 increases, and desired data can be written into the magnetic recording layer 103.

In the present embodiment, the magnetic pole of the magnetic head 16, specifically, the main magnetic pole 66 of the write head 58 of the head 44, is made different in magnetic pole width depending on the position of the magnetic head 16 (write head 58). The position of the magnetic head 16 here is a relative position in a direction in which the plurality of magnetic disks 12 are coaxially arranged with a predetermined interval therebetween, that is, a direction (parallel direction) in which the plurality of magnetic heads 16 are arranged with a predetermined interval therebetween in correspondence with the plurality of magnetic disks 12. Hereinafter, the state in which the magnetic disk 12 and the magnetic head 16 are aligned in this manner is referred to as a stacked state, and the direction in which these are coaxially aligned is referred to as a stacking direction. That is, the magnetic disk 12 and the magnetic head 16 are arranged in a stacked state along the stacking direction. The magnetic pole width is the width of the main magnetic pole 60 in the cross track direction WT, which is the width WP of the leading end portion 60a, and the width direction of the recording track formed in the magnetic recording layer (recording layer) 103 of the magnetic disk 12.

The number of heads 16 corresponds to the number of discs 12. Fig. 7 schematically shows the following manner as an example: the 9 magnetic disks 12 are coaxially arranged in a stacked state, and 18 magnetic heads 16, which are arranged one on each of both surfaces of each magnetic disk 12, are arranged in a stacked state.

These magnetic disks 12 are arranged in a stacked state from a magnetic disk 12a located on the base side (lower side in fig. 7) of the housing 11 to a magnetic disk 12i located on the cover side (upper side in fig. 7). In response to this, the magnetic heads 16 are arranged in a stacked state from the magnetic head 16a positioned on the base side of the housing 11 to the magnetic head 16r positioned on the cover side.

The width WP of the main pole 60 is wider in the magnetic head 16 located in the outer layer farther from the vicinity of the center in the stacking direction. That is, the magnetic head 16 having the wider width WP is disposed in the outer layer which is farther from the vicinity of the center in the stacking direction (the outer position which is farther from the vicinity of the center in the parallel direction). The center in the stacking direction is an intermediate position in the stacking direction (parallel direction) defined by the plurality of magnetic heads 16 arranged in a stacked state. In other understanding, the center in the stacking direction corresponds to the position of the center (pitch) of the torsion generated in the shaft rotatably supported by the bearing portion 24 of the carriage assembly 20.

In the example shown in fig. 7, the position between the magnetic head 16i and the magnetic head 16j among the 18 magnetic heads 16a to 16r arranged in a stacked state corresponds to the center in the stacking direction. Therefore, these magnetic heads 16i and 16j correspond to the magnetic head 16 near the center in the stacking direction. Hereinafter, these magnetic heads 16i and 16j are referred to as center heads as appropriate to distinguish them from the other magnetic heads 16. In addition, if the number of the magnetic heads 16 is an odd number, the magnetic head 16 disposed at the center in the stacking direction corresponds to a center head. The magnetic head 16a is the magnetic head 16 located at the outermost layer on the substrate side in the stacking direction, and the magnetic head 16r is the magnetic head 16 located at the outermost layer on the cap side in the stacking direction. Hereinafter, these

magnetic heads

16a and 16r positioned at the outermost layers are referred to as outer heads as appropriate to distinguish them from the other magnetic heads 16.

Of the 18 magnetic heads 16, the width WP of the main pole 60 of the write head 58 is wider in the outer layer magnetic head 16 that is farther from the vicinity of the center in the lamination direction. Fig. 8 is a diagram showing an example of the value of the width WP (write core width) of the main pole 60 of the write head 58 of the 18 heads 16a to 16 r. In fig. 8, 1 of Head No corresponds to the

magnetic Head

16a, and 18 of Head No corresponds to the magnetic Head 16r in ascending order from now on.

As shown in fig. 8, the width WP of the main pole 60 is such that the magnetic heads 16i and 16j, which are the center heads, are the narrowest (smaller), the magnetic heads 16, which are the outer heads, are gradually wider toward the outer layers with respect to the center head in the stacking direction, and the

magnetic heads

16a and 16r, which are the outer heads, are the widest (larger). In the example shown in fig. 8, the amount of change in the width WP (write core width) is 1nm, but the amount of change is not limited to this. The amount of change may not be uniform, and the amount of change in the width WP may be varied from the center head to the outer head.

Here, for example, as the width WP of the main pole 60 is wider, the write spread (write penetration) to the adjacent track due to the repeated recording (writing) to the magnetic disk 12 is more likely to increase. Therefore, for example, adjustment such as setting the track width large is required. The positioning accuracy of the magnetic head 16 is likely to be deteriorated as the magnetic head is positioned closer to the base and the cover of the housing 11, that is, closer to both sides (outermost layer) in the stacking direction. In this case, the outer-layer magnetic disk 12 in the stacking direction having relatively low positioning accuracy is likely to perform recording beyond the adjacent tracks in one recording (writing) operation, and therefore, the track pitch needs to be set to be larger than the track pitch of the inner-layer magnetic disk 12 having relatively high positioning accuracy.

In contrast, in the present embodiment, instead of adjusting the track pitch, the width WP of the main pole 60 is made narrower as the center head is used, and the width WP of the main pole 60 is made wider as the outer head is used. Therefore, even when the positioning accuracy is worse than that of the center head as the outer head becomes, the recording capacity of the magnetic disk 12 can be increased. In addition, since the magnetic heads 16 having different widths WP of the main pole 60 are mixed in one HDD10, the yield of the magnetic heads 16 can be improved.

Thus, for example, the recording capacity of the magnetic disk 12 can be similarly increased by narrowing the width WP of the main pole 60 as the center head is approached and widening the width WP of the main pole 60 as the outer head is approached, and by narrowing the width of the magnetic characteristic of the main pole 60 as the center head is approached and widening the width of the magnetic characteristic of the main pole 60 as the outer head is approached. That is, in this case, the magnetic head 16 having the wider magnetic characteristic of the main pole 60 is disposed in the outer layer that is farther from the vicinity of the center in the stacking direction (the outer position that is farther from the vicinity of the center in the parallel direction). For example, regarding the width of the magnetic characteristics of the main pole 60, the magnetic heads 16i and 16j as the center heads are the narrowest (small), and the magnetic heads 16 positioned on the outer layer side with respect to the center heads in the stacking direction are gradually wider, and the

magnetic heads

16a and 16r as the outer heads are the widest (large). The amount of change in the width of the magnetic characteristic may not be uniform, and the amount of change may vary from the center head to the outer head.

The width of the magnetic characteristic of the main pole 60 is: when the magnetic head 16, specifically, the write head 58 is used to magnetically record the recording track, the read head 54 can appropriately read the width of the recording region in the cross track direction WT of the magnetic characteristics of the recording region. As shown in fig. 9, the width is determined as the amplitude of the off-track profile (50%) of the recording signal output when the off-bias voltage of STO65 is turned off (off). The cross-track position and the signal output shown in fig. 9 are examples, and are not limited to these.

Next, an HDD according to another embodiment will be described. In other embodiments described below, the basic configuration is the same as that of embodiment 1 described above. Therefore, the characteristic configuration of another embodiment different from embodiment 1 will be described below, and the same components will not be described below with reference to the corresponding drawings in embodiment 1.

(embodiment 2)

In embodiment 2, the magnetic head 16 is tested for its performance before being assembled to the HDD10, and is classified into a plurality of groups according to the test results. In the present embodiment, the error rate of the magnetic head 16 is detected. The error rate is a ratio of a recording pattern in which recording is performed beyond a recording track adjacent to the recording track (hereinafter referred to as an adjacent recording track) in one recording (writing) operation of the recording track of the magnetic disk 12 by the write head 58.

Fig. 10 is a diagram schematically showing a relationship between the number of times of recording (Write count) and the Error Rate (Error Rate) for adjacent recording tracks. In fig. 10, the magnetic heads 16 are classified into three groups A, B, C, and schematically show the relationship between the number of times of recording to adjacent recording tracks in each group and the error rate after the number of times of recording. In the example shown in fig. 10, the error rate is deteriorated in the order of the group a, the group B, and the group C. Specifically, as the number of times of recording increases, for example, when the number of times of recording N is exceeded, the error rate of the group B becomes significantly deteriorated as compared with the group a, and further, the error rate of the group C becomes significantly deteriorated as compared with the group B.

In the present embodiment, among a plurality of groups into which the magnetic heads 16 are classified according to the error rates in this way, the group to which the magnetic head 16 having the higher error rate belongs is arranged in the outer layer which is farther from the vicinity of the center in the stacking direction (the outer position which is farther from the vicinity of the center in the parallel direction).

Here, as shown in fig. 7, a system in which 18 magnetic heads 16a to 16r are arranged is assumed. In this case, the magnetic heads 16a to 16r are classified into a plurality of groups every predetermined number according to the error rate. As an example, the 18 magnetic heads 16a to 16r are classified into three groups A, B, C corresponding to fig. 10 every 6. Specifically, the

heads

16g, 16h, 16i, 16j, 16k, and 16l belong to the group a. The

heads

16d, 16e, 16f, 16m, 16n, 16o belong to the group B. The

heads

16a, 16b, 16C, 16p, 16q, 16r belong to the group C.

Therefore, in the example of the embodiment shown in fig. 7, the 6 magnetic heads 16g to 16l belonging to the group a having the lowest error rate are arranged in the vicinity of the center in the stacking direction. On the base side (positions of the

heads

16d, 16e, and 16 f) and the cap side (positions of the

heads

16m, 16n, and 16 o) of the

heads

16, 3 heads 16 belonging to the group B having the error rate lower than the group a are arranged, respectively. Further, 3 magnetic heads 16 belonging to the group C are arranged on the base side (positions of the

magnetic heads

16a, 16b, and 16C) and the cap side (positions of the

magnetic heads

16p, 16q, and 16 r) of the magnetic heads 16, respectively.

Thus, the error rate of the magnetic head 16 increases from the center head to the outer head in the stacking direction in groups. The number of groups into which the magnetic heads 16 are classified is not limited to 3, and may be 2, or 4 or more. Here, as for the magnetic heads 16 arranged in the stacking direction, the positioning accuracy is more likely to be deteriorated as the external heads are, and it is preferable to increase the pitch of the recording tracks (track pitch). On the other hand, the outer head can relax the edge characteristics (error rate degradation when performing magnetic recording on adjacent recording tracks) in response to the need to widen the track pitch. In addition, the magnetic head 16 having such a high error rate can also improve the linear recording density and reduce the track pitch density. Therefore, in the present embodiment, instead of adjusting the track pitch, the groups of the magnetic heads 16 having a higher error rate are arranged in the outer layer which is farther from the vicinity of the center in the stacking direction. Therefore, the recording capacity of the magnetic disk 12 can be increased.

(embodiment 3)

In embodiment 3, the magnetic disk 12 is tested for its performance before being assembled to the HDD10, and is classified into a plurality of groups according to the test results. In the present embodiment, an index value indicating overwrite characteristics (OW) of the disk 12 is detected. The overwrite characteristics are indexed by the amplitude difference between the recording patterns before and after overwriting when a recording pattern of a frequency different from the recording pattern is overwritten on the recording pattern (pattern) of a certain frequency, and the quality (difficulty of writing) is determined from the value. For example, in the case of perpendicular magnetic recording, since a low-frequency signal is difficult to write than a high-frequency signal, a value representing in dB that a signal is not completely erased when writing of a low-frequency signal is performed after writing of a high-frequency signal may be used as an index of overwrite characteristics.

Fig. 11 is a diagram showing an example of a case where the disks 12 are classified based on the overwrite characteristics (OW). In the example shown in fig. 11, the disks 12 are classified into 5 groups (groups) according to the range of values of the overwrite characteristic, that is, the degree of difficulty of writing. In this case, Gr1 is a group to which the disk 12 that is most difficult to overwrite belongs, and Gr5 is a group to which the disk 12 that is most easily overwritten belongs in ascending order below. The threshold value between the groups shown in fig. 11 is an example, and is not limited to the illustrated value, and may be set arbitrarily.

In the present embodiment, among a plurality of groups into which the disks 12 are classified according to the overwrite characteristics (OW), the group to which the disk 12 having higher overwrite characteristics belongs is arranged in an outer layer which is farther from the vicinity of the center in the stacking direction (an outer position which is farther from the vicinity of the center in the parallel direction).

Here, as shown in fig. 7, a mode in which 9 magnetic disks 12a to 12i are arranged is assumed. In this case, the magnetic disks 12a to 12i are classified into a plurality of groups per predetermined number of pieces according to overwrite characteristics. As an example, 9 magnetic disks 12a to 12i are classified into 5 clusters (Gr1 to Gr5) corresponding to fig. 11. Specifically, the disk 12e belongs to Gr1 (20. ltoreq. OW < 23). Similarly, the

disks

12d and 12f belong to Gr2 (23. ltoreq. OW < 26), the

disks

12c and 12g belong to Gr3 (26. ltoreq. OW < 29), the

disks

12b and 12h belong to Gr4 (29. ltoreq. OW < 32), and the

disks

12a and 12i belong to Gr5 (32. ltoreq. OW < 35).

Therefore, in the embodiment example shown in fig. 7, the magnetic disk 12e belonging to Gr1 having the lowest overwrite characteristic is arranged near the center in the stacking direction. On the base side and the cover side of the magnetic disk 12e, there are arranged the magnetic disks 12 belonging to Gr2, Gr3, and Gr4 having higher overwrite characteristics than Gr1, respectively. The

magnetic disks

12a and 12i belonging to Gr5 having the highest overwrite characteristic are disposed as outermost layers in the stacking direction.

Thus, the overwrite characteristics of the magnetic disk 12 are increased in groups from the vicinity of the center to the outermost layer in the stacking direction. Therefore, for example, unlike the above-described

embodiments

1 and 2, even when the width WP of the main pole 60 of the magnetic head 16 is substantially the same or the error rate is substantially the same, the recording capacity of the magnetic disk 12 can be increased.

(embodiment 4)

In embodiment 4, the head amplifier IC30 makes the recording current for exciting the main pole 60 different depending on the position of the magnetic head 16 (write head 58) in the stacking direction. Specifically, when magnetic recording (data writing) is performed on the magnetic disk 12, the recording current supplied from the recording current supply circuit (recording current supply unit) 91 to the 1 st recording coil 70 and the 2 nd recording coil 72 is controlled by the main controller 90.

Fig. 12 is a flowchart showing an example of the control of the recording current (recording current control process) by the main controller 90. As shown in fig. 12, at the time of data writing to the disk 12, the host controller 90 receives from the host 95: a write command instructing data writing to the magnetic disk 12 (ST 1).

When receiving a write command, the main controller 90 selects a write destination of data, determines a recording track of the magnetic disk 12 to be written with data based on servo information or the like. Thereby, the main controller 90 specifies the position in the stacking direction (parallel direction) of the magnetic head 16 for writing (magnetically recording) data to the specified recording track (ST 2).

Next, the main controller 90 writes data to the magnetic disk 12 that has been determined as the write destination of the data. Specifically, the HDC96 causes the head amplifier IC30 to perform signal processing of data via the R/W channel 94. At this time, the head amplifier IC30 changes the magnitude of the recording current supplied from the recording current supply circuit 91 to the 1 st recording coil 70 and the 2 nd recording coil 72 in accordance with the position of the magnetic head 16 (write head 58) in the stacking direction. Thereby, the main pole 60 is excited, and the amount of magnetic flux flowing through the main pole 60 changes. The memory 80 of the main controller 90 stores, for example, a predetermined table relating the relationship between the position of the magnetic head 16 (write head 58) in the stacking direction and the optimum value of the recording current at that position. In controlling the recording current, the MPU97 sets an optimum value of the recording current at a position of the magnetic head 16 (write head 58) in the stacking direction from the table, and passes the value as a parameter to the head amplifier IC 30.

In the present embodiment, the recording current supply circuit 91 increases (increases) the recording current for exciting the main pole 60 more for the magnetic head 16 (outer head) disposed on the outer layer side in the stacking direction (outer position in the parallel direction) than for the magnetic head 16 (central head) disposed near the center in the stacking direction (parallel direction) (ST 3). The recording current for exciting the main pole 60 is increased, and the same effect as widening the width WP of the main pole 60 is achieved. Therefore, by increasing the recording current for exciting the main pole 60 as compared with the center head as the outer head becomes, the same effect as increasing the width WP of the main pole 60 as compared with the center head becomes can be obtained.

Thus, for example, unlike the above-described

embodiments

1 and 2, even when the width WP of the main pole 60 of the magnetic head 16 is substantially the same or the error rate is substantially the same, the recording capacity of the magnetic disk 12 can be increased. Further, for example, unlike the above-described embodiment 3, even when the overwrite characteristics (OW) of the magnetic disk 12 are substantially the same, the recording capacity of the magnetic disk 12 can be increased.

While several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and spirit of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

Claims

1. A magnetic disk device is provided with:

a plurality of magnetic disks having recording layers and arranged coaxially with spaces therebetween; and

a plurality of magnetic heads having magnetic poles for generating a recording magnetic field in a direction perpendicular to the recording layer, the magnetic heads being arranged at intervals along the parallel direction of the magnetic disks,

among the plurality of magnetic heads, the magnetic head having a wider magnetic pole width of the magnetic pole in the width direction of the recording track formed in the recording layer, or the magnetic head having a wider area width in the width direction, which is capable of reading the magnetic characteristics of the area where the magnetic recording is performed on the recording layer by the magnetic head, is disposed at a position further away from the vicinity of the center in the parallel direction.

2. The magnetic disk apparatus according to claim 1,

the head has the magnetic pole and a write shield opposite the magnetic pole with a write gap,

the magnet has a shield-side end face that opens the write gap to oppose the write shield,

the magnetic pole width is a width in the width direction of the shield side end face.

3. The magnetic disk apparatus according to claim 1,

the region width is defined based on an off-track curve of a recording signal output in the magnetically recorded region.

4. A magnetic disk device is provided with:

among a plurality of groups into which the magnetic heads are classified according to a ratio of magnetic recording beyond an adjacent recording track adjacent to the recording track when the magnetic heads perform magnetic recording on the recording tracks of the recording layer, the group to which the magnetic heads having a higher ratio belong is arranged at an outer position that is farther from the vicinity of the center in the parallel direction.

5. A magnetic disk device is provided with:

in a plurality of groups into which the disks are classified based on index values representing overwrite characteristics of the disks, the groups to which the disks belong are arranged at positions that are farther from the vicinity of the center in the parallel direction than the groups to which the disks belong, the index values being higher.

6. A magnetic disk device is provided with:

a plurality of magnetic disks having recording layers and arranged coaxially with spaces therebetween;

a plurality of magnetic heads having magnetic poles for generating a recording magnetic field in a direction perpendicular to the recording layer, the magnetic heads being arranged at intervals along a direction in which the magnetic disks are arranged; and

a recording current supply unit for supplying a recording current for exciting the magnetic pole to flow a magnetic flux,

the recording current supply unit increases the recording current more for the magnetic head arranged at a position further outward in the parallel direction than for the magnetic head arranged near the center in the parallel direction.